This invention relates to the separation of liquid mixtures. It further relates to the separation of hydrocarbon-alcohol azeotropes using anhydrous ammonia as the entraining agent. In one embodiment, it relates to the distillation of cyclohexane from an azeotropic mixture of cyclohexane and t-butyl alcohol.
In certain industrial chemical processes, liquid azeotropic mixtures of a hydrocarbon and an alcohol are used as solvent mediums or are obtained as a byproduct. Such mixtures may be the preferred solvents because of physical or chemical properties of the azeotropic mixture which are not characteristic of the individual components. For example, in the process for preparing mixed, isomeric unsaturated dinitriles from the reaction of acrylonitrile and isobutylene, a step in the production of fiber-grade polyamides, an azeotropic mixture of cyclohexane and t-butyl alcohol is the preferred reaction solvent because it is a stable composition at the reaction conditions and because the mixture has a much lower freezing point than either of its components, each of which freezes above 32.degree. F. and is thus an impractical solvent for a plant process. It has been found that this azeotropic mixture is particularly difficult to separate into its components because the mixture forms solid solutions, making it impossible to separate by crystallization as well as by distillation.
It is thus an object of this invention to provide a method for separating azeotropic mixtures of a hydrocarbon and an alcohol. It is a further object to provide a method for the distillation of cyclohexane from an azeotropic mixture of cyclohexane and t-butyl alcohol.